工具欄未顯示應用名稱和后退按鈕

Question

因此，由於我在前面發布的工具欄陰影問題，我想到了如何刪除它的想法。 現在至少沒有陰影，但是沒有活動名稱或后退按鈕。 見下圖

這是content.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:elevation="0dp"

    app:layout_behavior="@string/appbar_scrolling_view_behavior"
    tools:context="hr.app.liftme.liftmehr.Vjezbe"
    tools:showIn="@layout/activity_vjezbe">


    <android.support.design.widget.AppBarLayout
        android:layout_height="wrap_content"
        android:layout_width="match_parent"
        android:text="Vježbe"
        android:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar">


        <include
            android:layout_height="wrap_content"
            android:layout_width="match_parent"
            layout="@layout/toolbar_layout"
            >

        </include>





        <android.support.design.widget.TabLayout
            android:id="@+id/tabLayout"
            app:tabMode="scrollable"
            app:tabGravity="fill"
            android:layout_width="match_parent"
            android:layout_height="wrap_content">


        </android.support.design.widget.TabLayout>

        <android.support.v4.view.ViewPager

            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:id="@+id/viewPager"
            android:background="#ffffff">

        </android.support.v4.view.ViewPager>





    </android.support.design.widget.AppBarLayout>

</LinearLayout>

這是toolbar.xml

<?xml version="1.0" encoding="utf-8"?>

<android.support.v7.widget.Toolbar
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:background="?attr/colorPrimary"
    android:minHeight="?attr/actionBarSize"
    android:fitsSystemWindows="true"
    android:id="@+id/toolBar"

    app:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar">


</android.support.v7.widget.Toolbar>

Java文件

package hr.app.liftme.liftmehr;

import android.os.Bundle;
import android.support.design.widget.FloatingActionButton;
import android.support.design.widget.Snackbar;
import android.support.design.widget.TabLayout;
import android.support.v4.view.ViewPager;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.view.View;

public class Vjezbe extends AppCompatActivity {
    private Toolbar toolbar;
    TabLayout tabLayout;
    ViewPager viewPager;
    ViewPagerAdapter viewPagerAdapter;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_vjezbe);
        toolbar = (Toolbar) findViewById(R.id.toolbar);
        if (toolbar == null){


        setSupportActionBar(toolbar);
            getSupportActionBar().setTitle("Vježbe");
            getSupportActionBar().setHomeButtonEnabled(true);
        getSupportActionBar().setDisplayHomeAsUpEnabled(true);
        getSupportActionBar().setElevation(0);
    }


        tabLayout = (TabLayout)findViewById(R.id.tabLayout);
        viewPager = (ViewPager)findViewById(R.id.viewPager);
        viewPagerAdapter = new ViewPagerAdapter(getSupportFragmentManager());
//here are the fragments, not going to copy all of that

如您所見，我在java文件中嘗試了if語句，但是沒有用。

我想念什么？

Answer 1

問題

if (toolbar == null)

解決方案

使用!null檢查而不是null

 if (toolbar != null){

        setSupportActionBar(toolbar);
        getSupportActionBar().setTitle("Vježbe");
        getSupportActionBar().setHomeButtonEnabled(true);
        getSupportActionBar().setDisplayHomeAsUpEnabled(true);
        getSupportActionBar().setElevation(0);
    }

編輯

 // toolbar
    Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
    setSupportActionBar(toolbar);

    if (getSupportActionBar() != null){
        //Your code
    getSupportActionBar().setTitle("Vježbe");
    getSupportActionBar().setHomeButtonEnabled(true);
    getSupportActionBar().setDisplayHomeAsUpEnabled(true);
    getSupportActionBar().setElevation(0);
    }

工作

通過添加android:elevation="0dp" 。

Answer 2

刪除if(toolbar==null)因為只有當工具欄為null時，此條件才為true

並使其

 if (toolbar != null){
        setSupportActionBar(toolbar);
        getSupportActionBar().setTitle("Vježbe");
        getSupportActionBar().setHomeButtonEnabled(true);
        getSupportActionBar().setDisplayHomeAsUpEnabled(true);
        getSupportActionBar().setElevation(0);
    }

Answer 3

只需將如下代碼添加到您的onCreate事件中即可：

@Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.example_activity);//set view

        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);// initial your tool bar 
        setSupportActionBar(toolbar);//set tool bar
        getSupportActionBar().setDisplayHomeAsUpEnabled(true);//allow back button
        getSupportActionBar().setDisplayShowHomeEnabled(true);//Show back arrow
        getSupportActionBar().setLogo(R.mipmap.yourlogo);//set logo
        getSupportActionBar().setDisplayUseLogoEnabled(true);//enable log

}